Description of the Prior Art
Under certain circumstances, it is desirable to have a source of visible light that is portable and not electrically activated. Light can be provided by the mixture of chemicals, wherein the luminosity is solely the result of a chemical reaction. Such light is known as chemiluminescent light.
Chemiluminescent light can be used in a variety of emergency situations, such as where a source of electrical power has failed. Its portability makes it also an excellent choice for underwater use. Since chemiluminescence is cold light, it is highly effective around inflammable agents such as spilled gasoline, etc.
The art of generating light from chemical energy is continually in search of processes and compositions which will emit light of improved intensity and duration (most chemiluminescence has a finite lifetime) as contrasted with known processes and compositions.
Prior to this invention, as disclosed in U.S. Pat. No. 3,749,679, Rauhut, there have been a number of variables which influence the chemiluminescent reaction, light output, intensity, and duration.
The term "light" as used herein, is defined as electromagnetic radiation at wavelengths falling between about 350 and 800 millimicrons.
The term "chemiluminescent composition" as used herein, means a mixture which emits light by a chemical reaction.
The term "oxalate component" as used herein, means an aromatic ester of oxalic acid in a suitable solvent.
The term "peroxide component" as used herein, means a solution of a hydrogen peroxide compound, a hydroperoxide compound, or a peroxide compound in a suitable solvent.
The term "fluorescer" as used herein, means a fluorescent compound that when used as a part of the chemiluminescent composition, shifts the energy so as to emit light between 350 and 800 millimicrons.
The term "catalyst" as used herein, means a compound which when mixed to the chemiluminescent composition, accelerates the reaction.
As previously mentioned, there are a number of variables to alter the performance, i.e. light output, of the chemiluminescent composition. These variables are as follows:
1. Oxalate structure PA1 2. Oxalate concentration PA1 3. Peroxide structure PA1 4. H.sub.2 O.sub.2 concentration PA1 5. Fluorescer structure PA1 6. Fluorescer concentration PA1 7. Catalyst structure PA1 8. Catalyst concentration PA1 9. Selection of solvents for components PA1 10. Reaction temperature, and PA1 11. Additives PA1 a. Esters, such as ethyl acetate, ethyl benzoate, dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, methyl formate, triacetin, diethyloxalate, and dioctyl terephthalate. PA1 b. Aromatic hydrocarbons such as benzene, toluene, ethyl benzene, and butylbenzene. PA1 c. Chlorinated hydrocarbons such as chlorobenzene, chloroform, and carbon tetrachloride.
The effect of the variables is discussed in subsequent paragraphs.
(1) Oxalate Structure
The oxalate ester generally used is a bis (phenyl) oxalate ester having the formula: ##STR1## in which the phenyl groups (P) are substituted by (1) at least one carbalkoxy group of the formula ##STR2## in which R is (a) an alkyl group, or (b) a substituted alkyl group, where said substituents are selected from the group comprising fluoro, chloro, trifluoromethyl, alkoxy, cyano,carbalkoxy, and phenyl; and in which (2) the phenyl groups, P, are substituted by at least two additional substituents selected from the group comprising fluoro, chloro, bromo, cyano, trifluoromethyl, carbalkoxy, nitro, alkoxy, alkoxymethyl, methyl, and higher alkyl.
The preferred species are: bis (2, 4, 5-trichloro-6-carbobutoxyphenyl) oxalate and bis (6-carbopentoxy-2, 4, 5-trichlorophenyl) oxalate, also bis (2, 4, 5, trichloro-6-carboxyphenyl) oxalate as disclosed in U.S. Pat. No. 3,816,326, Bollyky.
(2) Oxalate Concentration
The oxalate concentration of reaction mixture may vary widely from 0.01M to 1.5M (moles per liter diluent).
(3) Peroxide Structure
The peroxide employed in the composition may be obtained from any hydroperoxide compound. Examples are: sodium peroxide, sodium perborate, urea peroxide, and hydrogen peroxide. The preferred composition is anhydrous hydrogen peroxide in a suitable solvent such as an ether, an ester, or an aromatic hydrocarbon.
(4) Peroxide Concentration
The hydrogen peroxide concentration in the peroxide component may range from about 0.2M to about 15M.
(5) Fluorescer Structure
The fluorescent compounds used are numerous; and they may be defined broadly as those which do not readily react on contact with the peroxide or with the ester of oxalic acid. Typical suitable fluorescent compounds are those which have a spectral emission falling between 330 millimicrons and 800 millimicrons and which are at least partially soluble in any of the diluents in the subsequent paragraphs. Among these are the conjugated polycyclic aromatic compounds having at least 3 fused rings, such as: anthracene, substituted anthracene, benzanthrancene, phenanthracene, substituted phenanthracene, napthacene, substituted naphthacene, pentacene, substituted pentacene, and the like.
Numerous other fluorescent compounds having these properties are well known in the art. Many of these are fully described in "Fluorescence and Phosphorescence" by Peter Pringsheim, Interscience Publishers, Inc., New York, N.Y. 1949. Other fluorescers are described in "The Handbook of Fluorescence Spectra of Aromatic Molecules" second edition by I. Berlman, Academic Press, New York, N.Y. 1971.
The preferred fluorescers for the chemiluminescent composition are: 1-chloro-9,10-bis (phenylethynyl) anthracene, and 2-chloro-9,10-bis (phenylethynyl) anthracene as disclosed in U.S. Pat. No. 3,888,786, Maulding. Also 9,10-diphenylanthracene, and 9,10-diphenyl-9,10-dihydroanthracene.
(6) Fluorescer Concentration
The fluorescer concentration may range from about 0.0002M to about 0.03M. Preferably the concentration ranges from about 0.001M to about 0.01M.
(7) Catalyst Structure
Catalyst structures are those which are weakly basic salt type such as sodium salicylate, and tetrabutylammonium salicylate as disclosed in U.S. Pat. No. 3,775,336, Bollyky. Other preferred catalysts are rubidium chloride, lithium chloride, lithium sulfate, and tetrabutylammonium perchlorate as disclosed in U.S. Pat. No. 3,704,231, Bollyky.
(8) Catalyst Concentration
Preferably, the catalyst is included in the peroxide component to control the lifetime of the chemiluminescent system. The concentration of catalyst used in the peroxide compound may range from about 10.sup.-5 M to about 10.sup.-2 M, preferably from about 10.sup.-4 M to about 10.sup.-3 M.
(9) Selection of Solvents for Components
The chemiluminescent system is basically a two component system. The first being the oxalate component with the fluorescer in a suitable solvent. The second being the peroxide component with the catalyst in a suitable solvent.
1. Typical diluents, or solvents which can be used for the oxalate component are:
Of these solvents, the preferred are ethyl benzoate, dibutyl phthalate, and dimethyl phthalate.
2. Diluents for the peroxide component are broadly primary, secondary, and tertiary alcohols, such as ethyl, hexyl, 2 ethyl hexyl, tertiary butanol, and 3 methyl 3 pentanol. Esters such as dimethyl phthalate and dioctyl phthalate, and ethers such as diethyl ether, and diamyl ether.
(10) Reaction Temperature
Light intensities increase and lifetimes decrease with increasing temperature. It has been found that the superior intensity of chemiluminescence is maintained at a temperature of between about -40.degree. C. and 75.degree. C., preferably between about 0.degree. C. and 50.degree. C.
(11) Additives
The addition of a small amount of polyethylene oxide (0.1 to 5% by weight), and/or a small amount of cellulose acetate butyrate (approx. 0.4% weight) has shown to increase the light output and duration of the chemiluminescent system. U.S. Pat. No. 3,994,820, Maulding and Rauhut.
Also the peroxide component is better stabilized for storage with the addition of about 0.004M 2, 4, 6-tri-tert-butylphenol. U.S. Pat. No. 4,064,064, Rauhut.